Torque-limiting clutch

ABSTRACT

A torque-limiting device is provided which has a rotatably mounted driving member and a driven member. The driving member is connected to a spring cage member through a torsion spring. A clutch spring is disposed to provide frictional driving engagement between the cage member and the driven member. The clutch spring and the driving member are provided with coacting surfaces to release the driving engagement between the cage member and the driven member when a given angular displacement between the cage member and the driving member occurs. The angular displacement between the driving member and the cage member will be proportional to the torque applied by virtue of the torsion spring connection between the driving member and the cage member.

United States Patent [72] lnventor Herbert Mould, Ill

Bloomfield, NJ. [21] Appl. No. 884,489 {22] Filed Dec. 12, 1969 [45]Patented Nov. 9, 1971 [73] Assignee Vari-Typer Corporation Hanover, NJ.

[54] TORQUE-LIMITING CLUTCH 8 Claims, 3 Drawing Figs.

[52] US. Cl 192/56 C, 192/74 [51] Int. Cl ..F16d 13/08, F16d 43/21 [50]Field of Search 192/41 S, 56 C, 74 [56] References Cited UNITED STATESPATENTS l,56l,537 11/1925 Hayes l92/56CX Primary Examiner-Allan D.l-lerrmann Attorneys-Russell L. Root and Ray S. Pyle l92/56CX 192/56CXABSTRACT: A torque-limiting device is provided which has a rotatablymounted driving member and a driven member. The driving member isconnected to a spring cage member through a torsion spring. A clutchspring is disposed to provide frictional driving engagement between thecage member and the driven member. The clutch spring and the drivingmember are provided with coacting surfaces to release the drivingengagement between the cage member and the driven member when a givenangular displacement between the cage member and the driving memberoccurs. The angular displacement between the driving member and the cagemember will be proportional to the torque applied by virtue of thetorsion spring connection between the driving member and the cagemember.

PATENTEDunv 9 ISYI 3,618,730

HERBERT Mouz 0 122' JNVE'N'TUR BY 7% El AT TUE/\EY TORQUE-LIMITINGCLUTCH BACKGROUND OF THE INVENTION This invention relates to devices inwhich a positive driving connection between a driving member and adriven member is desired up to a predetermined driving torque load, andwhich will allow slippage between the driving member and-driven memberat a higher torque load than this predetermined value.

The invention is generally applicable. to anysituation wherein it isdesired to drive a member to develop torque up to a predetenninedmaximum and prevent transmission of torque, (i.e., allow slippage) abovethe predeterminedtorque level.

There have been many prior art devices accomplishing this purpose. Thepresent invention constitutes an improvement over the prior art devicesin that a relatively simple, inexpensive yet reliable torqueJimitingdevice is provided which will function precisely at a given, andpreferably anadjustable, torque level.

SUMMARY OFTI-IE INVENTION An advantage of this invention is that driveis accomplished through a wound torsion spring, and a predetermineddegree of angular displacement between the driver and driven'memhers isemployed to trigger a complete release of s spring clutch.

Briefly, the present invention is comprised of a driving member and adriven member. Acage member is provided and transmission means in theform of a torsion .spring drivingly interconnects the driving memberwith'the cage member. The transmission means provides a given change inrelationship between the cage member and the driving member at a giventorque level. Releasable engagement means in the form of a clutch springdrivingly interconnects the driven member and the cage member. Theclutch spring and cage member include cooperatingmeans disposed torelease the driving interconnection of the clutch spring between thedriven member and the cage member when-the given change in relationshipbetween the position of the cage member and the driving member occurs.

DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal sectional view of atorque-limiting device according to this invention;

FIG. 2 is a sectional view taken substantially along the planedesignated by the line 2-2 of FIG. 1; and FIG. 3 is a sectional viewtaken substantially along the plane designated by the line 3-3 ofFIG. 1. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to thedrawing, a torque-limiting device is shown which is adapted to drivinglyinterconnect a drive collar joumaled on shaft 11 to a driven pulley 12so that the drive collar will drive the pulley up to a predeterminedtorque level, above which level slippage will occur. The drive collar 10is connected to any suitable power source, such as anelectric motor,(not shown) for providing rotation thereto. The direction of rotation ofthe device is shown 'by the arrows in FIGS. 2 and 3.

An annular driving disc 13 is keyed to the drive collar 10 by a key 14and key slot 15. The drive collar 10 and driving disc 13 together definea driving member.

A spring cage 16 is provided which surrounds the drivecollar 10. Thespring cage is comprised of an inner sleeve section 18 and an outer ringsection 20 interconnected by set screws, one of which is shown at 22.The spring cage 16 is formed in two parts to allow for adjustment of thetorque load at which the device will slip, as will be explainedpresently. However, if no such adjustment is required, the spring cagecould be made of a single component rather than of separate sleeve andring portions.

A torsion spring 24 is wound around the drive collar 10 and has oneendthereof 26 disposed in an aperture 28 formed in the driving disc 13(FIGS. 1 and 3), and the other end 30 thereof disposed in an aperture 32formed in the sleeve section' 18 of the spring cage 16 (FIGS. 1 and2)."The torsion spring 24 provides transmission means in the form of aresilient drive connection between the drive collar 10 and the springcage 16, and upon rotation of the drive collar will cause the springcage 16 to rotate therewith.

A clutchspring 36 surrounds the sleeve 18. The clutch spring'36 has oneend 38 disposed in an aperture 40 formed in the ring section 20 of thespring'cage 16 (FIGS. 1 and 2) and the opposite end 42 disposed in anelongated slot 44 formed in the driving disc 13 (FIGS. 1 and 3).As canbest be seen in FIG. 3, the slot 44 has one end surface 45 whichconstitutes an 15 actuating surface, and the end 42 of the clutch spring36'is normally spaced from this actuating su'rface'45.

The clutch'spring 36 is formed of a flat wire "and is configured so thatit is normally held by its inherent expansion into tight contact withboth the inner surface 46-of the ring section'20,'and the inner surface48 of the driven pulley 12, so that in this'there will be a drivingconnection between the spring cage 16 and the drivenpulley 12 whendriven in the direction of rotation shown by the arrows in FIGS. 2 and3.

OPERATION When the drive collarl0 is rotated, a driving torque will beapplied to the spring cage 16 through the torsion spring '24 spring cage16 and the driven pulley 12, the pulley will rotate with the spring cage16.

With respect to the driving of the spring cage l6'by the drive collarl0, the torsion spring provides a'resilient driving connectiontherebetween, and any torque developed will cause an angulardisplacement between thecollar and cage proportional'to the torque;i.e., the cage will lag'behind the drive collar an amount proportionalto the'torque. This proportional angular displacement is utilized tointerrupt the driving interconnection between the driven pulley l2 anddrive collar 10 at a given torque level in the following manner:

The driving disc 13 is keyed to the drive collar 10, so that theactuating disc will be displaced angularlywithrespect' to the springcage16 the same as the drive collar. This angular displacement is aclockwise direction-of the driving'disc 13 with respect to the springcage 16 as viewed in FIG. 3. Since the clutch spring 36 is in engagementwith the cage,'it will proportional to the torque. This displacementwill move the actuating surface 45 of the slot 44 closer to the end 42of the clutch spring 36. The'greater the torque, thegreater the angulardisplacement and hence the closer actuating surface 45 willcome to theend 42 of the clutch spring 36 until-a torque is reached which willcause the actuating surface 45 to engage theend 42 of the spring.Further movement will wind down" or partially collapse spring 36. Whenthe spring is wound down, it decreases in diameter, and when thediameter is decreased, the drive interconnection afforded by the springbetween cage and pulley will cease. This loss of driving interconnectionoccurs at a given angular displacement of the cage with respect to theactuating disc, which angular displacement represents a given torque.Hence, any torqueb'elow this level will be transmitted, but torque aboutthis level will not be.

As explained above, the two piece construction of the spring cage 16allows the torque value at which the device will slip to be adjusted.The adjustment relies on the fact that the amount of torque required toproduce a given angular relationship is a function of the torsionpreload of the torsion spring 24. The greater the preload of the spring,the greater the torque required to produce a given angular displacement.The torque preload in the spring 24 can be changed by rotating thesleeve portion 18 of the spring cage 16 with respect to both the ringportion 22 thereof and the drive collar 10.

In order to effect such a change, the set screws 22 are loosened Thedrive collar and ring portion are held in a fixed relative position, andthe sleeve portion 18 is rotated in a direction which will tend topreload the torsion spring 24. This preload of the spring 24 willcorrespondingly increase the torque required to effect a given angulardisplacement between the spring cage 16 and drive collar 10. Since theposition of the ring portion 22 and drive collar 10 is unchanged, theend 42 of the spring 36 will remain in its same relative position in theslot 44 when the sleeve is rotated. Hence, the same total angulardisplacement between the spring cage 16 and drive collar 10 will berequired to cause the actuating surface 45 to engage end 42 of thespring. However, a greater torque is required to attain this angulardisplacement.

What is claimed is:

1. A torque device comprising:

a driving member;

a cage member;

transmission means drivingly interconnecting said driving member andsaid cage member disposed to provide a given change in relationshipbetween at least a portion of said cage member and said driving memberat a given torque;

a driven member;

releasable clutch spring means drivingly interconnecting said drivenmember and said cage member, said releasable engagement means and saidportion of said cage member including coactable portions of said drivingmember and said clutch spring disposed to release the drivinginterconnection of said engagement means between said driven member andsaid cage member when said given change in relationship between saidportion of cage member and said driving member occurs.

2. The invention as defined in claim 1 wherein said engagement meansinterconnecting said driven member and said cage member includes clutchspring means.

3. The invention as defined in claim 1 wherein said transmission meansincludes means to cause a given angular displacement of said cage memberand said driving means at a given torque level.

4. The invention as defined in claim 1 wherein said transmission meansincludes means to cause relative displacement of said cage member andsaid driving member proportional to the torque.

5. The invention as defined in claim 1 wherein said transmission meansincludes torsion spring means drivingly interconnecting said cage memberand said driving member.

6. The invention as defined in claim 1 further characterized by meansdisposed to adjust the torque level at which the driving connectionbetween the cage member and driven member is released.

7. The invention as defined in claim 1 wherein said transmission meansincludes a torsion spring, and means disposed to adjust the preload ofsaid torsion spring, whereby to adjust the torque at which the drivingconnection is released.

8. The invention as defined in claim 1 further characterized by saidengagement means interconnecting said cage member and said driven memberincluding clutch spring means, and said cooperating means includescoactable portions of said driving member and said clutch spring, andwherein said transmission means includes torsion spring means, and saiddriven member and said torsion spring and said cage member are mountedto provide a relative angular displacement of said cage member and saiddriving member proportional to the torque, and wherein said coactingportions of said clutch spring and said driving member coact at a givenangular relationship to release said driving connection of said clutchspring and said driven member.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,618,730 Dated November 9, 1971 Inventor(s) Herbert Mould III It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 3, lines 27 and 30, "engagement", in each of the lines, shouldread clutch spring Column 3, cancel lines 3 1 and 35;

Column cancel line 1;

Column 4, cancel lines 21, 22, 23, 2 4, and 25 and substitute Theinvention as defined in claim 1 further characterized in that saidtrans- Signed and sealed this 13th day of June 1972.

(SEAL) Attest:

EDWARD M. FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents )RM po'wso USCOMM-DC scan-pe Q U 5, GBVIRNMENT PRINTINGQFFICE '9; 0-366!!

1. A torque device comprising: a driving member; a cage member;transmission means drivingly interconnecting said driving member andsaid cage member disposed to provide a given change in relationshipbetween at least a portion of said cage member and said driving memberat a given torque; a driven member; releasable clutch spring meansdrivingly interconnecting said driven member and said cage member, saidreleasable engagement means and said portion of said cage memberincluding coactable portions of said driving member and said clutchspring disposed to release the driving interconnection of saidengagement means between said driven member and said cage member whensaid given change in relationship between said portion of cage memberand said driving member occurs.
 2. The invention as defined in claim 1wherein said engagement means interconnecting said driven member andsaid cage member includes clutch spring means.
 3. The invention asdefined in claim 1 wherein said transmission means includes means tocause a given angular displacement of said cage member and said drivingmeans at a given torque level.
 4. The invention as defined in claim 1wherein said transmission means includes means to cause relativedisplacement of said cage member and said driving member proportional tothe torque.
 5. The invention as defined in claim 1 wherein saidtransmission means includes torsion spring means drivinglyinterconnecting said cage member and said driving member.
 6. Theinvention as defined in claim 1 further characterized by means disposedto adjust the torque level at which the driving connection between thecage member and driven member is released.
 7. The invention as definedin claim 1 wherein said transmission means includes a torsion spring,and means disposed to adjust the preload of said torsion spring, wherebyto adjust the torque at which the driving connection is released.
 8. Theinvention as defined in claim 1 further charActerized by said engagementmeans interconnecting said cage member and said driven member includingclutch spring means, and said cooperating means includes coactableportions of said driving member and said clutch spring, and wherein saidtransmission means includes torsion spring means, and said driven memberand said torsion spring and said cage member are mounted to provide arelative angular displacement of said cage member and said drivingmember proportional to the torque, and wherein said coacting portions ofsaid clutch spring and said driving member coact at a given angularrelationship to release said driving connection of said clutch springand said driven member.